In recent years, wireless terminals such as a cellular phone using a battery as a power source and a mobile PC installed with a communication device widely spread to be used in a mobile communication system. In accordance with the trend, the effort to elongate the continuous operation time of these wireless terminals has been made by using various energy saving technologies.
Meanwhile, a wireless terminal consumes the most power in transmitting a signal in the total power consumption. The power required for transmission in a conventional wireless terminal is determined by the intensity or quality of the signal transmitted by a radio base station and received by the wireless terminal in a mobile communication system.
As an example of prior art, patent document 1 relates to a radio communication system, wherein transmission power is determined on the basis of measured intensity of a received signal.
Patent Document 1: JP 07-226710 A